The Near-Infrared Mapping Spectrometer (NIMS) on Galileo
observed Io during the spacecraft's three close fly-bys in
October and November 1999, and February 2000. The spectral
range of NIMS (0.7 to 5.2 microns) allows the instrument to
map the thermal emission from Io's many volcanic regions, as
well as absorption bands seen in reflected sunlight. NIMS
data obtained during the fly-bys were used to make detailed
maps of the temperature distribution within volcanic
centers, maps of the SO2 distribution on the surface, and of
an yet-unidentified absorption band detected at 1 micron.
The distribution of SO2 on the surface will be discussed by
Doute' et al. (this volume). This paper will present the
results of our thermal mapping of different hot spots, and
of the relationship between the absorption near 1 micron and
surface color, albedo, and proximity to hot spots. We find
that hot spots such as Pele and Tvashtar have high
temperatures that may be consistent with ultramafic magmas,
while the temperatures are Loki are significantly lower,
consistent with large expanses of cooling lavas erupted
perhaps a few months earlier. Prometheus and Amirani have
long lava flows, probably tube-fed and, at least in the case
of Prometheus, responsible for the generation of a plume as
the lava interacts with SO2 frost. These volcanic regions
are different from each other and provide examples of the
variety of volcanic processes taking place on Io. Portions
of this work were performed at JPL under contract with NASA.